Damping force adjustable fluid pressure shock absorber

Abstract

A piston coupled to a piston rod is fitted in a sealed cylinder in which oil is contained. During an extension stroke of the piston rod, a damping force is generated by an extension-side valve body, and at the same time, a valve-opening pressure of an extension-side main valve is adjusted by an inner pressure in an extension-side backpressure chamber. During a compression stroke of the piston rod, a damping force is generated by a compression-side valve body, and at the same time, a valve-opening pressure of a compression-side main valve is adjusted by an inner pressure in a compression-side backpressure chamber. A simple structure is realized by using a common guide bore for guiding the extension-side valve body and the compression-side valve body. Check valves are provided at both ends of the guide bore and communication passage are provided through the extension-side valve body and the compression-side valve body so that an amount of excess oil due to a movement of the extension-side valve body and the compression-side valve body can be expelled, thereby improving responsiveness of the shock absorber.

1. A damping force adjustable fluid pressure shock absorber, comprising:
 a cylinder in which a fluid is sealingly contained; 
 a piston slidably fitted in the cylinder so as to divide an inside of the cylinder into two chambers; 
 a piston rod coupled to the piston and extending to an outside of the cylinder; 
 an extension-side flow passage and a compression-side flow passage through which the two chambers in the cylinder are in communication with each other; and 
 a damping force generating mechanism for generating a damping force by controlling fluid flows in the extension-side flow passage and the compression-side flow passage, 
 wherein the damping force generating mechanism comprises: 
 an extension-side main valve provided at the extension-side flow passage, 
 an extension-side backpressure chamber for adjusting a valve-opening pressure of the extension-side main valve, 
 an extension-side bypass flow passage through which the two chambers in the cylinder are in communication with each other, 
 an extension-side presure control valve provided at the extension-side bypass flow passage and adapted to be opened by receiving a pressure in the extension-side bypass flow passage, 
 a compression-side main valve provided at the compression-side flow passage, 
 a compression-side backpressure chamber for adjusting a valve-opening pressure of the compression-side main valve, 
 a compression-side bypass flow passage through which the two chambers in the cylinder are in communication with each other, and 
 a compression-side pressure control valve provided at the compression-side bypass flow passage and adapted to be opened by receiving a pressure in the compression-side bypass flow passage, 
 the extension-side bypass flow passage introducing a pressure of an upstream side of the extension-side pressure control valve into the extension-side backpressure chamber, 
 the compression-side bypass flow passage introducing a pressure of an upstream side of the compression-side pressure control valve into the compression-side backpressure chamber, 
 the extension-side pressure control valve and the compression-side pressure control valve comprising: 
 a guide bore shared by the two valves, the guide bore having one end in communication with one of the two chambers in the cylinder and an opposite end in communication with the other of the two chambers in the cylinder, 
 a first valve body slidably fitted in the guide bore, and adapted to be seated on a seat surface provided in the guide bore and to be opened by receiving a pressure in one of the extension-side bypass flow passage and the compression-side bypass flow passage, 
 a second valve body slidably fitted in the guide bore, and adapted to be seated on a seat surface provided at the first valve body and to be opened by receiving a pressure in the other of the extension-side bypass flow passage and the compression-side bypass flow passage, 
 a damping force adjuster for adjusting valve-opening pressures of the first valve body and the second valve body by biasing the first valve body and the second valve body in valve-closing directions thereof, 
 a first check valve provided at the one end of the guide bore, and allowing only a fluid flow from one end side of the first valve body and the second valve body to the one of the two chambers in the cylinder, and 
 a second check valve provided at the opposite end of the guide bore, and allowing only a fluid flow from an opposite end side of the first valve body and the second valve body to the other of the two chambers in the cylinder, and 
 an axially extending communication passage provided through the first valve body and the second valve body, the axially extending communication passage allowing communication between the one end side of the first valve body and the second valve body, and the opposite end side of the first valve body and the second valve body. 
 
     
     
       2. The damping force adjustable fluid pressure shock absorber according to  claim 1 , wherein the damping force adjuster comprises a proportional solenoid actuator. 
     
     
       3. The damping force adjustable fluid pressure shock absorber according to  claim 2 , further comprising a biasing unit provided between the valve bodies for biasing the first valve body and the second valve body in a direction in which the valve bodies are spaced apart from each other. 
     
     
       4. The damping force adjustable fluid pressure shock absorber according to  claim 2 , wherein:
 the first valve body includes a small diameter portion on one end side thereof, the small diameter portion adapted to be seated on the seat surface provided in the guide bore, and a large diameter portion on an opposite end side thereof, the large diameter portion adapted to be guided by the guide bore; and 
 the second valve body includes a small diameter portion on one end side thereof, the small diameter portion adapted to be seated on the seat surface provided at the first valve body, and a large diameter portion on an opposite end side thereof, the large diameter portion adapted to be guided by the guide bore. 
 
     
     
       5. The damping force adjustable fluid pressure shock absorber according to  claim 2 , further comprising a valve seat member provided in the guide bore so as to be axially movable, the valve seat member including an end surface serving as the seat surface which abuts against the first valve body. 
     
     
       6. The damping force adjustable fluid pressure shock absorber according to  claim 5 , wherein one of the first check valve and the second check valve is provided in the valve seat member. 
     
     
       7. The damping force adjustable fluid pressure shock absorber according to  claim 2 , wherein the guide bore extends in an axial direction of the piston rod. 
     
     
       8. The damping force adjustable fluid pressure shock absorber according to  claim 1 , further comprising a biasing unit provided between the valve bodies for biasing the first valve body and the second valve body in a direction in which the valve bodies are spaced apart from each other. 
     
     
       9. The damping force adjustable fluid pressure shock absorber according to  claim 8 , wherein:
 the first valve body includes a small diameter portion on one end side thereof, the small diameter portion adapted to be seated on the seat surface provided in the guide bore, and a large diameter portion on an opposite end side thereof, the large diameter portion adapted to be guided by the guide bore; and 
 the second valve body includes a small diameter portion on one end side thereof, the small diameter portion adapted to be seated on the seat surface provided at the first valve body, and a large diameter portion on an opposite end side thereof, the large diameter portion adapted to be guided by the guide bore. 
 
     
     
       10. The damping force adjustable fluid pressure shock absorber according to  claim 8 , further comprising a valve seat member provided in the guide bore so as to be axially movable, the valve seat member including an end surface serving as the seat surface which abuts against the first valve body. 
     
     
       11. The damping force adjustable fluid pressure shock absorber according to  claim 10 , wherein one of the first check valve and the second check valve is provided in the valve seat member. 
     
     
       12. The damping force adjustable fluid pressure shock absorber according to  claim 8 , wherein the guide bore extends in an axial direction of the piston rod. 
     
     
       13. The damping force adjustable fluid pressure shock absorber according to  claim 1 , wherein:
 the first valve body includes a small diameter portion on one end side thereof, the small diameter portion adapted to be seated on the seat surface provided in the guide bore, and a large diameter portion on an opposite end side thereof, the large diameter portion adapted to be guided by the guide bore; and 
 the second valve body includes a small diameter portion on one end side thereof, the small diameter portion adapted to be seated on the seat surface provided at the first valve body, and a large diameter portion on an opposite end side thereof, the large diameter portion adapted to be guided by the guide bore. 
 
     
     
       14. The damping force adjustable fluid pressure shock absorber according to  claim 13 , further comprising a valve seat member provided in the guide bore so as to be axially movable, the valve seat member including an end surface serving as the seat surface which abuts against the first valve body. 
     
     
       15. The damping force adjustable fluid pressure shock absorber according to  claim 14 , wherein one of the first check valve and the second check valve is provided in the valve seat member. 
     
     
       16. The damping force adjustable fluid pressure: shock absorber according to  claim 13 , wherein the guide bore extends in an axial direction of the piston rod. 
     
     
       17. The damping force adjustable fluid pressure shock absorber according to  claim 1 , further comprising a valve seat member provided in the guide bore so as to be axially movable, the valve seat member including an end surface serving as the seat surface which abuts against the first valve body. 
     
     
       18. The damping force adjustable fluid pressure shock absorber according to  claim 17 , wherein one of the first check valve and the second check valve is provided in the valve seat member. 
     
     
       19. The damping force adjustable fluid pressure shock absorber according to  claim 17 , wherein the guide bore extends in an axial direction of the piston rod. 
     
     
       20. The damping force adjustable fluid pressure shock absorber according to  claim 1 , wherein the guide bore extends in an axial direction of the piston rod.